The present invention relates to a digital phase detector for use in connection with synchronizing the transition of clock pulses for retiming the received NRZ (nonreturn to zero) data at the center of the unit bit interval of the data to be retimed.
Conventionally, a circuit for bit synchronism comprises an open loop-type retiming circuit wherein the transition of a clock pulse extracted from a data is manually adjusted to occur at the center of the unit bit interval of received data. As a result, the transition of the clock pulse extracted from the data can not be placed automatically at the center of the unit bit interval of the data. The circuit also consists of an accurate phase complementary circuit, so that the retiming performance thereof depends upon the accuracy and the temperature chracteristics of the constituting elements. Also, recently developed self-adjusting retiming circuits have a drawback of limiting the data bit-transmitting rate, because they frequently generate jitter and produce a phase information in the form of a pulse width.